MATLAB: Is it possible to use an array in an if statement

ifMATLAB

Hi, I need to compare each member of an array against a fixed value and then modify that memeber according to whether it is smaller or larger than the fixed value. I can loop through the array to do this, but I'm trying to speed the code up and was wondering whether you could simply operate on the array directly? I've tried it and I get the same operation on each member irrespective of whether it is smaller or larger than the fixed value.
The code I've used is as follows:
if Gr<10^5
Nu_G=0.5.*Gr.^0.25;
else
Nu_G=0.13.*Gr.^0.33;
end
Can anyone advise whether this is possible or whether there may be any other way to achieve the same effect i.e. avoid the loop and/or speed up the code
Thanks,
Rebecca

Best Answer

Nu_G = zeros(size(Gr));
Nu_G(Gr<10^5) = 0.5.*Gr(Gr<10^5).^0.25;
Nu_G(Gr>=10^5) = 0.13.*Gr(Gr>=10^5).^0.33;
This is potentially slower than the loop method. In your if/else you only need to test Gr<10^5 once for every element, in the vectorized version you need to test twice.